Method of determining the center of gravity of ships



Jim. 13, 1931. AA. J. couGHTRY METHOD oF DETERMINING THE CENTER oF GRAVITY 013l sHIPs` Filed Dec.` 27, 1929 A )w r Y reza 25 `or light, consists in h Patented 1.3, *1931-i UNITED* .STATES PATENT" ori-ics ARTHUR .racen ooUGn'rnY, on vPort'rsmouTH,.ivi-vv HAMPSHIRE rnacieron or nnrnnnmme cENfrEn or. GRAVITY 'or 'smrs Application mec December er, was. i serial 1ra/416,926.

This invention pertains to a method l or process of determining the center of gravity of a ship and to apparatus useful in the practice of such method or process. In loadmg a 5 ship it is desirable to keep the center of gravity within a certain range of position in orderv to insure stability and to` prevent capsizing. Heretofore, so far asis known to me,there has been-no practical method by which the centerof gravity of a loaded ship could be accurately determined Without delay ust previous to sailing on ,each voyage, although approximate -results have been obtained` by locating the center of gravity of the shlp when unloaded orlight, and guessing at'the position thereof afterloading. 'Howevelg this isa-mere approximation to the correct result, and involves the initial step. of deter-v 1 .mining the center of gravity ofthe unloaded ship which is itself, according to usual.

gle of heel induced. by the known weight. v

Havingthus determined -the angle of heel, and knowing the weight ofthe ship, the weight employed in heeling it, and the posi-` .ton of the weight with re tral vertical plane of the ship', .it-is possible to calculate accuratel the center of gravity of -t e loa edor unloaded ship'.l However, this method of-determining".A type Y verticallongitudinal central-I lane. of the ship indicated by the lineW- point on this line'is found the center 'of '90' l gravity G-of'theships hull, and when the Y the center of gravit is not of practical value as applied t'oa loa ed ship just previous to ,4 .each sailing-or voyage because it is diicult,

expensive and time co v In accordance wi, h the-present ocess I 'am able to determine the center o gravity of the loaded ship, directly with .45 amount of trouble' and expense, and without substantial loss (if time, and as' respects' the i loaded ship, the present 'method provides an accuracy of determination not heretofore known so that' by the adoption of this method "0 thes ililty or lack of stability of the loaded rence tothe censition of the ship can readily v"be ascertained before the ship leaves the pier previous to each voyage, thus avoiding danger of capsizing.

In the acgompanying ldrawings I have illustrated diagrammatically one desirable s equence; of steps in performing my process, as well as certain structural details useful in the practical application of' the process, and-in the drawings:

transverse section Aof a ship unloaded and equipped for the performance of my proce; Fig. 2 is a similar view, but 'showing the ship fully loaded;

Fig. 3 1s `a enerally similarview, showing the loaded ship tipped to permit determina-A -tion of the center of gravity according to my method;

Figa. is s diagram illustrating the relation anc of a Heating body; Y f

. `g. 5 is a'siinilar diagram, showing the eiects of'tipping-the Boating body; Y Fig. 6 is a fragmentary sectional view illustratin one convenient method of attach-v the oat or pontoon toa ships side and for releasing it quickly therefrom in the vprac- `tieeofmyprocess; -Y Fig. `7 's a Vfragmentary view, to smaller scale than'Fig. 6, illustrating.. another way go of lattaching the float, .the-latter being endA elevation, and

Fig. als s view 'of theses; O f Fig. '7,' de; tached from the ship and in side elevation.

Referring 'first to Figs. 4 and- 5, S repre- 85 sente in outline a ships hull of conventional with'the water level at L and. withl the is' floating on an even keel, the' center Y' examplejby placing aheavy weight P close to one side ofthe ships hull, as yshowrlin is unchanged but the center of buoyancy movesrelatively thereto, overto 'some point Vme Fig. 1 is a conventional diagrammatic@ of the center of gravity andcenter of buoy- 70 l At some?! zj f such as B'. In this position the flotation force acts vertically up through the center of buoyancy B along the line C-D, and

this line makes an angle 9 with the central longitudinal plane W-X. The point at which the line C-D intersects the line W--X is here referred to as the metacenter, and so long as this metacenter is at a substantial. distance above the, center of gravity, there is always present a turning couple tending to restore the ship to its normal level position. However, if the center of gravity be raised, as for example by placing the cargo too high, .it may nearly approach or rise above the metacenter, in which event stabilit7 is totally lost and the turning couple invo ving the weight of the ship and the blllioyant force is now such as to capsiZe the s 1p.

It is thus evident that the center of gravity should be kept as low as necessary for safety, and in recent years it has been cus tomary for ship builders or owners to have the center of gravit of the ships hull deterinined, in order t at a proper margin of safety may be preserved -after the ship is loaded. Commonly this determination has been made by placing aweight, as shown in' Fig. 5( for example r om 20 to 100 tous, at one si e of the ship, thus causing it to heel or incline and then determining the angle 0 from which,' by mathematical calculation,

the location of the center of gravity could be v opposite sidesof the shi s hull, as for exdetermined. The manipulation of the very heavy weight necessary for this purpose is troublesome, ex ensive and time consuming and this meth is therefore wholly' unsuited to the direct determination of the center of gravity of a loaded ship, before each sailing.

In accordance-with the present invention' I proceed as illustrated, for example, in Figs. 1, 2 and 3, by first preparing suitable pontoons or floats 1 and 2 each of proper buoyancy or lifting capacity, for example, from 5 -to 100 tons. Obviously such pontoons may be made of convenient shape and material and of a size sugient 4to exert all of the force necessary for tipping .the ship even when loaded. When the ship arrives empty at port, these pontoons are floated against ample by a man in a sma l boat, and secured 'l thereto (suiliciently rigidly to prevent their hereinafter more fully described. The loademerging above the water when the ship is fully loaded) bydetachable connections, as

ing of the cargo now proceeds and as the pontoons are gradually forced deeper and deeper into the' water, they exert `an increasing lifting effect until, as shown in Fig. 2, when loading is complete,`the pontoons 1 and 2 are submerged, beneath the water level,'

and each exerts an upward lifting force due to its buoyancy acting substantially of sufficient intensity, if acting alone, to tip or heel the loaded ship.

After the ship is loaded, as Vshown in Fig. 2, the next step in the process is'to release one of the pontoons, for example pontoon 1, as shown in Fi 3, so'that it no longer supports its side o? the ship, although the other pontoon still continues to exert its upward force. This force, indicated by the line 4, Fig. 3,being unbalanced, tips the'ship so that the angle can readily be determined by usual methods; and since the point of application of the pontoon is known, and since its lifting effect can readly be calculated from its dimensions, the position of the center of ravity G of the ship can easily be calcu ated upon the basis of these and the other known factors. As soon as the angle 9 has been determined, the pontoon 2 is released, and the ship immediately resumes its normal position, and may proceed at once upon its voy- In Fig. 6 I have illustratedone mode of attaching the pontoons or floats to the ship', wherein the ships hull S is provided with a. depression or cavit in its side which receives the fixed brac et member 5. The pontoon is provided with projecting arms 6 and 7 spaced to admit the bracket 5 between them, the upper arm 6 and the upper wall of the bracket 5 being provided with aligned openings for the reception of theretaining bolt 8. Each pontoon is likewise preferably provided with one or more brace arms 9, the free end of the brace arm' being adapted to .engage within a socket or a ainst a suitable bracket on the ships side. releasing cable 10 is secured to the bolt 8 and above the Water'level.

extends up In applying the pontoon shown in Fig. 6, A

it is floated against the ships side and the arms 6 and 7 are caused to receive the bracket 5 between them. The bolt 8 is then inserted and this bolt, in combination with the brace" arm 9 and the arm 7, holds the pontoon in 1 In Figs. 7 and 8 I have illustrated another way of detachably securing the pontoon in place. In Fig.v 7, I have shown a section of the ships platin having a cavity 11 provided with an over anging lip 12. The pontoon 13 pontoon to tip the shipv as above hooks entering cavity 11, the brace is raised to the position of Fig. 7, but when it is desired to release the pontoon, the brace is pulled over sidewise until it no longer prevents upward movement of the pontoon. Y

As compared with the old process which makes use ofheavy extraneous weights in y obtaining the energy for heeling the ship, my

new process requires the application of no substanial force other than that developed in loading the ship, so that the expense involved in the operation is almost negligible.

While have hereinabove specifically described the use of two floats or pontoons, the

v process in its broader aspects may be carried out with the aid of a single pontoon which is attached to the unloaded ship, and which I"radually tips the ship during the loading `of the latter. When the ship is loaded, the angle of the tip may be noted for use in calculating the center of gravity, and as soon as lthe angle hasbeen determined the pontoon may be released, thereby immediately restoring the ship to an even keel. This modiica, tion of the rocess may be of utility where inadequate ockage accommodations make it difficult or impossible to employ a pontoon at each side of the shi Moreover, I contemplate that if conditions prevent attachment ofthe pontoon before loading begins, the process may be carried out by attaching one or two filled or partially filled pontoons and thenv during loading, pumping out one or both'pontoons so that when loading is complete the ship is or may be tipped in the same way as above described but without loss of time after loading is complete.

while I have here illustrated certain de! sirable forms of ontoon and attaching means therefor whic would be' useful in performing my improved process, I wish it to be understood that the invention is not limited to theseparticular details ofconstruction but that any equivalent means may beemployed for the purpose whereby the desired tipping force may be caused toact quickly and expeditiously.

I claim: 1. That method of gravity of a ship which comprises as steps .causing balanced lifting forces of known valship to exert a suddenly releasing `one of said pontoons whereby to permit thel other to tip the ship, and observing the angle ofv tip as a basis for calculating the center of gravity of the loaded shi 31.).That method of determining the position of the center of gravity of a ship which comprises as steps attaching to each side of the unloaded ship a lifting pontoon, loading the ship and thereby submerging the pontoons; whereby to create lifting forces due to the buoyancy of the submerged pontoons at each side `of the center line of the ship, and when the ship has been loadedto a predetermined extent suddenly releasin one of said pontoons so that the lifting orce of twenty-fourthday of December, 1929.

ARTHUR'JACOB COUGHTRY.

of determiningthe center ue to act upon a ship at predetermined point-s at its opposite sides during loadlng, increasing said forces progressively asthe loadin proceeds until either forceacting alone is su icient to tip the loaded ship to a'desired anceasve acting, whereby the loaded ship is suddenly causing onel of said forces to f A Signed by me at Portsmouth, N. H., this 

